There had been already a lot of discussions regarding the campaign visibility in the past: my personal favour would be to have them all 4 with their first mission ready from the beginning. in a campaign the order should be kept as the story evolves from mission to mission.
Reasons for doing it like in the current state could be that a player starting with the atlanteans or frisians might get frustrated and leave. So we try to guide him to better gameplay.

well, there are four tutorials, and the first two campaigns are marked as easier.

If a new player who knows nothing of the game skips all the tutorials, skip the easy missions and tries immediately on the hard part, he deserves to get burned

by the way, I just made empire missions 3 and 4 (didn't want to try the new missions before the official build), and I really like them. they are hard enough to be interesting, but easy enough that they should be doable by most people. they tell an interesting story. congrats to the designers

well, there are four tutorials, and the first two campaigns are marked as easier.

If a new player who knows nothing of the game skips all the tutorials, skip the easy missions and tries immediately on the hard part, he deserves to get burned

that is a very darwinistic view I think

by the way, I just made empire missions 3 and 4 (didn't want to try the new missions before the official build), and I really like them. they are hard enough to be interesting, but easy enough that they should be doable by most people. they tell an interesting story. congrats to the designers

Thanks for the flowers. But we always like people to test things before a release. So next time please feel encouraged to test any new mission before hand. There had been several testers been involved in making the missions better and more stable against alternative gameplay.